I think they are as per the nature of progressive springs, softer initially (so they absorb the small bumps easily) but then get firmer the further they get compressed. Makes for a nice compliant ride on tarmac but more capable offroad when under more extreme compression.
---------- Post added at 11:17 AM ---------- Previous post was at 11:12 AM ----------
I fitted them myself, took me all day Saturday (I also fitted SVC Bump stops). I was on my own and the springs are heavy. It would be better with 2 people as trying to get the springs in place without damaging anything like Brake lines road speed sensor etc. is not easy on your own.
I would say that a decent shop with the right equipment should be able to do it in 3-4 hours.